Microwave remote sensing of sea ice in the AIDJEX Main Experiment

During the AIDJEX Main Experiment, April 1975 through May 1976, a comprehensive microwave sensing program was performed on the sea ice of the Beaufort Sea. Surface and aircraft measurements were obtained during all seasons using a wide variety of active and passive microwave sensors. The surface program obtained passive microwave measurements of various ice types using four antennas mounted on a tracked vehicle. In three test regions, each with an area of approximately 1.5 × 10⁴ m², detailed ice crystallographic, dielectric properties, and brightness temperatures of first-year, multiyear, and first-year/multiyear mixtures were measured. A NASA aircraft obtained passive microwave measurements of the entire area of the AIDJEX manned station array (triangle) during each of 18 flights. This verified the earlier reported ability to distinguish first-year and multiyear ice types and concentration and gave new information on ways to observe ice mixtures and thin ice types. The active microwave measurements from aircraft included those from an X- and L-band radar and from a scatterometer. The former is used to study a wide variety of ice features and to estimate deformations, while both are equally usable to observe ice types. With the present data, only the scatterometer can be used to distinguish positively multiyear from first-year and various types of thin ice. This is best done using coupled active and passive microwave sensing.We dedicate this work to our beloved friend William NordbergHe pioneered in microwave ice observations, and his brilliance and enthusiasm inspired all of us.     

A hybrid artificial neural network-numerical model for ground water problems

Numerical models constitute the most advanced physical-based methods for modeling complex ground water systems. Spatial and/or temporal variability of aquifer parameters, boundary conditions, and initial conditions (for transient simulations) can be assigned across the numerical model domain. While this constitutes a powerful modeling advantage, it also presents the formidable challenge of overcoming parameter uncertainty, which, to date, has not been satisfactorily resolved, inevitably producing model prediction errors. In previous research, artificial neural networks (ANNs), developed with more accessible field data, have achieved excellent predictive accuracy over discrete stress periods at site-specific field locations in complex ground water systems. In an effort to combine the relative advantages of numerical models and ANNs, a new modeling paradigm is presented. The ANN models generate accurate predictions for a limited number of field locations. Appending them to a numerical model produces an overdetermined system of equations, which can be solved using a variety of mathematical techniques, potentially yielding more accurate numerical predictions. Mathematical theory and a simple two-dimensional example are presented to overview relevant mathematical and modeling issues. Two of the three methods for solving the overdetermined system achieved an overall improvement in numerical model accuracy for various levels of synthetic ANN errors using relatively few constrained head values (i.e., cells), which, while demonstrating promise, requires further research. This hybrid approach is not limited to ANN technology; it can be used with other approaches for improving numerical model predictions, such as regression or support vector machines (SVMs).     

Interpretation of aeromagnetic data across the central crystalline shield area of Nigeria

Summary. A residual map of the total magnetic field (above 25 000 nT base) is presented for a portion of the central crystalline shield area of Nigeria and overlapping small portions of the Chad basin and the Benue rift (8°30'−12° 00'lat, and 7°−10°30' long). The map (based on a dataset digitized from recently released aeromagnetic sheets of Nigeria) leads to four results. (1) A magnetic boundary, evident on the map, separates the Younger Granite complexes into two groups. The groups are petrologically different, and the boundary may be a fault line with uplift to the south. (2) South of the boundary the map is dominated by a system of sub-parallel anomalies striking NE–SW, possibly representing major tectonic trends, and a set of fractures through which the Younger Granite complexes were intruded. The trend of the system parallels the Benue rift and lineaments in the oceanic crust off West Africa. (3) Negative magnetic anomalies lie over most of the known ring complexes, and over some suspected buried ring complexes and other intrusions. (4) 2½-and 3-D modelling shows that the larger complexes extend to 12 km depth, and the smaller ones to 6 km. They have nearly vertical sides, and magnetization contrasts range from 0.3 to 0.5 A m⁻¹.     

Gravitational radiation from strongly magnetized white dwarfs

The magnetic fields of white dwarfs distort their shape generating an anisotropic moment of inertia. A magnetized white dwarf that rotates obliquely relative to the symmetry axis has a mass quadrupole moment that varies in time, so it will emit gravitational radiation. The Laser Interferometer Space Antenna ( LISA ) mission may be able to detect the gravitational waves from two nearby, rapidly rotating white dwarfs.     

Public health impacts of climate change in Washington State: projected mortality risks due to heat events and air pollution

Illness and mortality related to heat and worsening air quality are core public health concerns associated with climate change projections. We examined the historical relationship between age- and cause-specific mortality rates from 1980 through 2006 and heat events at the 99th percentile of humidex values in the historic period from January 1, 1970 to December 31, 2006 in the greater Seattle area (King, Pierce and Snohomish counties), Spokane County, the Tri-Cities (Benton and Franklin counties) and Yakima County; the relative risks of mortality during heat events were applied to population and climate projections for Washington State to calculate number of deaths above the baseline (1980–2006) expected during projected heat events in 2025, 2045 and 2085. Three different warming scenarios were used in the analysis. Relative risks for the greater Seattle area showed a significant dose-response relationship between heat event duration and daily mortality rates for non-traumatic deaths for persons ages 45 and above, typically peaking at four days of exposure to humidex values above the 99th percentile. The largest number of projected excess deaths in all years and scenarios for the Seattle region was found for age 65 and above. Under the middle warming scenario, this age group is expected to have 96, 148 and 266 excess deaths from all non-traumatic causes in 2025, 2045 and 2085, respectively. We also examined projected excess deaths due to ground-level ozone concentrations at mid century (2045–2054) in King and Spokane counties. Current (1997–2006) ozone measurements and mid-twenty-first century ozone projections were coupled with dose-response data from the scientific literature to produce estimates overall and cardiopulmonary mortality. Daily maximum 8-h ozone concentrations are forecasted to be 16–28% higher in the mid twenty-first century compared to the recent decade of 1997–2006. By mid-century in King County the non-traumatic mortality rate related to ozone was projected to increase from baseline (0.026 per 100,000; 95% confidence interval 0.013–0.038) to 0.033 (95% CI 0.017–0.049). For the same health outcome in Spokane County, the baseline period rate of 0.058 (95% CI 0.030–0.085) was estimated increase to 0.068 (95% CI 0.035–0.100) by mid-century. The cardiopulmonary death rate per 100,000 due to ozone was estimated to increase from 0.011 (95% CI 0.005–0.017) to 0.015 (0.007–0.022) in King County, and from 0.027 (95% CI 0.013–0.042) to 0.032 (95% CI 0.015–0.049) in Spokane County. Public health interventions aimed at protecting Washington’s population from excessive heat and increased ozone concentrations will become increasingly important for preventing deaths, especially among older adults. Furthermore, heat and air quality related illnesses that do not result in death, but are serious nevertheless, may be reduced by the same measures.     

The relationship of Irgarol and its major metabolite to resident phytoplankton communities in a Maryland marina, river and reference area

The objectives of this study were to: (1) measure water column concentrations of Irgarol 1051 and its major metabolite GS26575 annually (2004-2006) during mid-June and mid-August at 14 sites in a study area comprised of three sub-regions chosen to reflect a gradient in Irgarol exposure (Port Annapolis marina, Severn River and Severn River reference area); (2) use a probabilistic approach to determine ecological risk of Irgarol and its major metabolite in the study area by comparing the distribution of exposure data with toxicity-effects endpoints; and (3) measure both functional and structural resident phytoplankton parameters concurrently with Irgarol and metabolite concentrations to assess relationships and determine ecological risk at six selected sites in the three study areas described above. The three-year summer mean Irgarol concentrations by site clearly showed a gradient in concentrations with greater values in Back Creek (400-500 ng/L range), lower values in the Severn River sites near the confluence with Back Creek (generally values less than 100 ng/L) and still lower values (<10 ng/L) at the Severn River reference sites at the confluence with Chesapeake Bay. A similar spatial trend, but with much lower concentrations, was also reported for GS26575. The probability of exceeding the Irgarol plant 10th centile of 193 ng/L and the microcosm NOEC (323 ng/L) suggested high ecological risk from Irgarol exposure at Port Annapolis marina sites but much lower risk at the other sites. There were no statistically significant differences among the three site types (marina, river and reference) with all years combined or among years within a site type for the following functional and structural phytoplankton endpoints: algal biomass, gross photosynthesis, biomass normalized photosynthesis, chlorophyll a, chlorophyll a normalized photosynthesis and taxa richness. Therefore, based on the above results, Irgarol adverse effects predicted from the plant 10th centile and the microcosm NOEC in the high Irgarol exposure area (Back Creek/Port Annapolis marina) were not confirmed with the actual field data for the receptor species (phytoplankton). These results also highlight the importance of unconfined field studies with a chemical gradient in providing valuable information regarding the responses of resident phytoplankton to herbicides.     

Absolute spectrophotomery of comets 1973XII and 1975IX: II. Profiles of the Swan bands

Absolute spectrophotometric measurements of the Swan bands of two comets have been compared with computed synthetic spectra using modern Franck-Condon and Hönl-London factors, and varying rotational, vibrational, and electronic excitation temperatures. Rotational and vibrational temperatures were obtained for the comets. Although the electronic excitation temperature and the molecular column density cannot be separated, a relationship is found between these two quantities. A review is made of recent determinations of column densities for CN in comets.     

Significance of lherzolite at the Etang de Lherz,central Pyrenees,southern France

Geologic relationships in the central Pyrenees of southern France demonstrate that lherzolite has been emplaced, as a plastic solid, into middle or upper Cretaceous calcareous rocks; that it has been eroded and clastic peridotite debris deposited in rocks of approximately the same age as those it intruded; and that it has also been juxtaposed against Cretaceous limestone or marble along or within the North Pyrenean fault zone. There are at least three types of late Cretaceous lherzolite breccias known from this region.Metamorphism of the country rock and penetrative deformation of the lherzolite and marble took place during shearing. Shearing was accompanied by an important period of motion (perhaps 85–100 m.y. ago) along the North Pyrenean fault and an associated thermal event which involved temperatures of 400 ± 100°C. Cretaceous metamorphism along the North Pyrenean fault zone was not due to forcible primary hot intrusion of lherzolite.     

A review of inverse methods in seismic site characterization

Journal of Seismology - Seismic site characterization attempts to quantify seismic wave behavior at a specific location based on near-surface geophysical properties, for the purpose of mitigating...     

Geographic information science and the analysis of place and health

The representation of place is a key theoretical advancement that geographic information science can offer to improve the understanding of environmental determinants of health, but developing robust computational representations of place requires a substantial departure from conventional notions of geographic representation in GIS. Unlike conventional GIS representations based on either objects or locations, we suggest that place representation should incorporate dynamic subjective, experiential, and relational aspects of place, as the influence of place on health behavior concerns not only the features that can be objectively observed at a particular location but also the environmental perceptions of the individual, as molded by biological, social, and experiential characteristics. In addition, assessments of environmental exposures on health outcomes should focus on individuals' time–activity patterns and microenvironment profiles, which form a potentially unique personalized exposure environment for each individual. Addressing these representational challenges via collaborative research has the potential to advance both geographic information science and health research.